Microelectronic device with a memory element utilizing stacked vertical devices

Abstract

An embodiment may include a method of forming a microelectronic device. The method may include forming a pair of transistors stacked vertically and connected in series, each of the pair of transistors are of the same type. The method may include forming a memory element including a first inverter containing a first inverter transistor and an access transistor. The first inverter transistor is connected to a power supply rail. The access transistor is connected to a bitline. The first inverter transistor is a first transistor of the pair of vertically stacked transistors and the access transistor is a second transistor of the pair of vertically stacked transistors. The pair of transistors are arranged substantially perpendicular to the plurality of layers.

What is claimed is: 
     
       1. A microelectronic device comprising a plurality of layers, the microelectronic device comprising:
 a first pair of n-channel transistors stacked vertically above a semiconductor substrate, each of the first pair of n-channel vertically stacked transistors are connected in series, wherein the first pair of n-channel vertically stacked transistors comprises a common nanowire, wherein the common nanowire comprises channel regions of both transistors of the first pair of n-channel vertically stacked transistors; 
 a memory element comprising a first inverter and a second inverter, 
 wherein the first inverter comprising a first inverter transistor and a first access transistor, the first inverter transistor is connected to a power supply rail buried in the semiconductor substrate, the first access transistor is connected to a bitline, 
 wherein the first inverter transistor is a first transistor of the first pair of n-channel vertically stacked transistors and the first access transistor is a second transistor of the first pair of n-channel vertically stacked transistors, wherein both the first inverter transistor and the first access transistor connected with a ground rail buried in the substrate, 
 wherein the first pair of n-channel vertically stacked transistors are arranged substantially perpendicular to the plurality of layers, 
 wherein channel regions of the first pair of n-channel vertically stacked transistors have an elongated cross section with a longitudinal axis and a transversal axis, wherein the longitudinal axis is longer than the transversal axis, wherein the elongated cross section is an elliptical shape, and 
 wherein the second inverter comprising a second inverter transistor and a second access transistor, wherein the second inverter transistor is a first transistor of a first pair of p-channel vertical transistors stacked one on top another above the substrate, and the second access transistor is a second transistor of the first pair of vertically stacked p-channel transistors, wherein both the second inverter transistor and the second access transistor are connected with the power supply rail; 
 a second pair of n-channel vertical transistors each comprising only one n-channel transistor, the second pair of n-channel vertical transistors are vertically aligned and are arranged substantially perpendicular to the plurality of layers of the integrated circuit; and 
 a second pair of p-channel vertical transistors each comprising only one p-channel transistor, the second pair of p-channel vertical transistors are vertically aligned and are arranged substantially perpendicular to the plurality of layers of the integrated circuit. 
 
     
     
       2. The microelectronic device according to  claim 1 ,
 wherein the second inverter transistor is arranged substantially perpendicular to the plurality of layers and connected to a further power supply rail. 
 
     
     
       3. The microelectronic device according to  claim 2 , wherein a gate of the first inverter transistor and a gate of the second inverter transistor are electrically connected to each other by a conductive element extending within a single layer of the microelectronic device. 
     
     
       4. The microelectronic device according to  claim 3 , wherein the connection to the gate of the first inverter transistor, the connection to the gate of the second inverter transistor and the conductive element are the same conductive element. 
     
     
       5. The microelectronic device according to  claim 1 , further comprising:
 an intermediate layer arranged between a first gate layer comprising the gate of the first inverter transistor and a second gate layer comprising the gate of the first access transistor, 
 wherein the memory element comprises a cross-coupling inverter cross coupled with the first inverter by means of a cross-coupling conductor, and 
 wherein the cross-coupling conductor includes a section extending within the intermediate layer. 
 
     
     
       6. A microelectronic device comprising a plurality of layers, the microelectronic device comprising:
 a first pair of n-channel transistors stacked vertically and connected in series; 
 a memory element including an inverter and a cross-coupling inverter, 
 wherein the inverter comprises a first inverter transistor connected to a ground rail buried in a semiconductor substrate of the microelectronic device and a second inverter transistor, 
 wherein the second inverter transistor is p-channel, 
 wherein the first inverter transistor is a first transistor of the first pair of n-channel vertically stacked transistors and the first pair of n-channel vertically stacked transistors are connected with the ground rail, 
 wherein a gate of the first inverter transistor and a gate of the second inverter transistor are electrically connected to each other by a single conductive element extending within a single layer of the microelectronic device, and 
 wherein the first inverter transistor and the second inverter transistor are substantially perpendicular to the plurality of layers; 
 an access transistor, wherein the access transistor is connected to a bitline, and a gate of the access transistor is connected to a wordline, wherein the access transistor is a second transistor of the first pair of n-channel vertically stacked transistors, wherein the second inverter transistor and the access transistor are connected with a power supply rail buried in the substrate, 
 wherein channel regions of the first inverter transistor, the second inverter transistor, and the access transistor have an elongated cross section with a longitudinal axis and a transversal axis, wherein the longitudinal axis is longer than the transversal axis, wherein the elongated cross section is an elliptical shape; 
 a second pair of n-channel vertical transistors each comprising only one n-channel transistor, the second pair of n-channel vertical transistors are vertically aligned and are arranged substantially perpendicular to the plurality of layers of the integrated circuit; and 
 a second pair of p-channel vertical transistors each comprising only one p-channel transistor, the second pair of p-channel vertical transistors are vertically aligned and are arranged substantially perpendicular to the plurality of layers of the integrated circuit. 
 
     
     
       7. The microelectronic device according to  claim 6 , further comprising:
 an intermediate layer arranged between a first gate layer comprising the gate of the first inverter transistor and a second gate layer comprising the gate of the access transistor, 
 wherein the memory element comprises a second inverter cross-coupled with the inverter by means of a cross-coupling conductor, and 
 wherein the cross-coupling conductor includes a section extending within the intermediate layer. 
 
     
     
       8. The microelectronic device according to  claim 6 , wherein the bitline extends perpendicular to the power supply rail. 
     
     
       9. The microelectronic device according to  claim 6 , wherein the wordline extends parallel to the power supply rail. 
     
     
       10. The microelectronic device according to  claim 6 , wherein the wordline extends in the same layer as the gate of the access transistor. 
     
     
       11. The microelectronic device according to  claim 6 , wherein the wordline and the gate of the access transistor are electrically connected in the same layer. 
     
     
       12. The microelectronic device according to  claim 6 , wherein the wordline and the bitline are provided in different layers of the integrated circuit. 
     
     
       13. A method of forming a microelectronic device comprising a plurality of layers, the method comprising:
 forming a first pair of n-channel transistors stacked vertically above a semiconductor substrate, each of the first pair of n-channel vertically stacked transistors are connected in series, wherein the first pair of n-channel vertically stacked transistors comprises a common nanowire, wherein the common nanowire comprises channel regions of both transistors of the first pair of n-channel vertically stacked transistors; 
 forming a memory element comprising a first inverter and a second inverter, 
 wherein the first inverter comprising a first inverter transistor and a first access transistor, the first inverter transistor is connected to a power supply rail buried in the semiconductor substrate, the access transistor is connected to a bitline, 
 wherein the first inverter transistor is a first transistor of the first pair of n-channel vertically stacked transistors and the first access transistor is a second transistor of the first pair of n-channel vertically stacked transistors, wherein both the first inverter transistor of the pair of n-channel transistors and the first access transistor are connected with a ground rail buried in the substrate, 
 wherein the first pair of n-channel vertically stacked transistors are arranged substantially perpendicular to the plurality of layers, 
 wherein channel regions of the first pair of n-channel vertically stacked transistors have an elongated cross section with a longitudinal axis and a transversal axis, wherein the longitudinal axis is longer than the transversal axis, wherein the elongated cross section is an elliptical shape, and 
 wherein the second inverter comprising a second inverter transistor and a second access transistor, wherein the second inverter transistor is a first transistor of a first pair of p-channel vertical transistors stacked one on top another, and the second access transistor is a second transistor of the first pair of vertically stacked p-channel transistors, wherein both the first inverter transistor and the second access transistor are connected with the power supply rail; 
 forming a second pair of n-channel transistors each comprising only one n-channel transistor, the second pair of n-channel vertical transistors are vertically aligned and are arranged substantially perpendicular to the plurality of layers of the integrated circuit; and 
 forming a second pair of p-channel vertical transistors each comprising only one p-channel transistor, the second pair of p-channel vertical transistors are vertically aligned and are arranged substantially perpendicular to the plurality of layers of the integrated circuit. 
 
     
     
       14. The method according to  claim 13 ,
 wherein the second inverter transistor is arranged substantially perpendicular to the plurality of layers and connected to a further power supply rail buried in the semiconductor substrate. 
 
     
     
       15. The method according to  claim 14 , wherein a gate of the first inverter transistor and a gate of the second inverter transistor are electrically connected to each other by a conductive element extending within a single layer of the microelectronic device. 
     
     
       16. The method according to  claim 15 , wherein the connection to the gate of the first inverter transistor, the connection to the gate of the second inverter transistor and the conductive element are the same conductive element. 
     
     
       17. The method according to  claim 13 , further comprising:
 forming an intermediate layer arranged between a first gate layer comprising the gate of the first inverter transistor and a second gate layer comprising the gate of the first access transistor, 
 wherein the memory element comprises a second inverter cross-coupled with the first inverter by means of a cross-coupling conductor, and 
 wherein the cross-coupling conductor includes a section extending within the intermediate layer. 
 
     
     
       18. A method of forming a microelectronic device comprising a plurality of layers, the method comprising:
 forming a first pair of n-channel transistors stacked vertically and connected in series; 
 forming a memory element including an inverter and a cross-coupling inverter, 
 wherein the inverter comprises a first inverter transistor and a second inverter transistor, 
 wherein the second inverter transistor is p-channel, 
 wherein the first inverter transistor is a first transistor of the first pair of n-channel vertically stacked transistors and the first pair of n-channel vertically stacked transistors are connected with a ground rail buried in a substrate, 
 wherein the first inverter transistor and the second inverter transistor are substantially perpendicular to the plurality of layers, and 
 wherein a gate of the first inverter transistor and a gate of the second inverter transistor are electrically connected to each other by a single conductive element extending within a single layer of the microelectronic device; and 
 forming an access transistor, wherein the access transistor is connected to a bitline, and a gate of the access transistor is connected to a wordline, wherein the access transistor is a second transistor of the first pair of n-channel vertically stacked transistors, wherein the second inverter transistor and the access transistor are connected with a power supply rail buried in the substrate, 
 wherein channel regions of the first inverter transistor, the second inverter transistor, and the access transistor have an elongated cross section with a longitudinal axis and a transversal axis, wherein the longitudinal axis is longer than the transversal axis, wherein the elongated cross section is an elliptical shape; 
 forming a second pair of n-channel vertical transistors each comprising only one n-channel transistor, the second pair of n-channel vertical transistors are vertically aligned and are arranged substantially perpendicular to the plurality of layers of the integrated circuit; and 
 forming a second pair of p-channel vertical transistors each comprising only one p-channel transistor, the second pair of p-channel vertical transistors are vertically aligned and are arranged substantially perpendicular to the plurality of layers of the integrated circuit. 
 
     
     
       19. The method according to  claim 18 , further comprising:
 an intermediate layer arranged between a first gate layer comprising the gate of the first inverter transistor and a second gate layer comprising the gate of the access transistor, 
 wherein the memory element comprises a second inverter cross-coupled with the inverter by means of a cross-coupling conductor, and 
 wherein the cross-coupling conductor includes a section extending within the intermediate layer. 
 
     
     
       20. The method according to  claim 18 , wherein the bitline extends perpendicular to the power supply rail. 
     
     
       21. The method according to  claim 18 , wherein the wordline extends parallel to the power supply rail. 
     
     
       22. The method according to  claim 18 , wherein the wordline extends in the same layer as the gate of the access transistor. 
     
     
       23. The method according to  claim 18 , wherein the wordline and the gate of the access transistor are electrically connected in the same layer.